The Development of the System that Analyzes Surface Cracks by the Influence Function Method

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In this study an effective evaluating system, by which the stress intensity factor, K,can be calculated easily for the 3-dimensional surface cracks subjected to arbitrarily distributed surface stresses on the cracked surface, was developed on the engineering work-station (EWS) by using the influence function method. The data base of the influence coefficients, Kij, has been obtained by a series of finite element analysis for various cracked members, such as, semi elliptical surface crack in a flat plate, quarter-elliptical surface crack in a flat plate, semi elliptical surface crack in a round bar, semi elliptical axial crack on the inner surface of hollow cylinder, circumferential surface crack in a hollow cylinder, semi elliptical surface crack in a flange type nozzle corner, and so on. Further more, in order to evaluate the K-value and the surface crack propagating in a complex stress field easily, a simulation system of fatigue crack propagation was developed on a personal computer by storing the Kij data base in the disc of the computer. It has been shown that the developed influence function method and the simulation systems are very useful to evaluate the stress intensity factor, K,and the surface crack propagating, for the surface cracks subjected to such complicated stress as residual stress, thermal stress, and it has been shown that the simulation system is useful to assess the residual life of the cracked structural components, and leak and/or failure probabilities. The results given by the system has been used in some standard of ASME and JSME.